Systems and methods for underground pipe installation and soil clearing

ABSTRACT

Systems and methods for installing pipe underground are disclosed. The system includes a pneumatic rammer configured to provide a percussive force to a section of pipe. The system also includes a main jacking frame coupled to the pneumatic rammer, the main jacking frame including a surface for contacting the section of pipe. The system also includes one or more hydraulic jacks coupled to the main jacking frame and configured to provide a hydraulic force to the section of pipe. The system also includes a set of tracks coupled to the main jacking frame, the set of tracks permitting the main jacking frame to slide in a longitudinal direction. An independently displaceable soil-clearing system can be included to clear dirt coming inside the pipe during the installation and add extra jacking force as needed.

RELATED APPLICATION

The application claims the benefit of U.S. Provisional PatentApplication No. 62/629,865, filed on Feb. 13, 2018 and entitled“Trenchless Pipeline Installation Method and Apparatus,” the entirecontents of which are hereby incorporated by reference in theirentirety.

TECHNICAL FIELD

The invention relates generally to systems and methods for installingunderground sections of pipe, including pipeline, gas mains, water andsewer lines, utility conduits and other utilities. More specifically,the invention relates to trenchless underground pipe installation, forexample using tools and methods that are suitable to install new pipesusing one or more of a hydraulic jacking force, pneumatic percussiveimpacts, and a dirt-extraction process of soil coming inside the pipeduring installation.

BACKGROUND

Various applications require the installation of underground pipesbetween two stations, such as between two manholes or the two sides of ahighway, without creating a trench between them.

Several prior techniques have been developed to accomplish trenchlessinstallation of carrier pipes (also known as product pipes) orprotective tubular casings (normally steel casings). Most of thesemethods are based on a static pushing force applied to the pipe againstthe ground; that is, pipes or casings are jacked through the ground bymeans of a hydraulically operated jacking unit from a previouslyprepared starting or entry shaft to a target shaft. In general, all ofthese pipe jacking-based installations (e.g., horizontal auger boringmachines, guided boring machines, and micro-tunneling machines, amongothers) require a rotating shield or cutting head at the front of thefirst pipe, in order to cut the ground in front of it, as well as asystem to transport the spoils to the starting pit. Moreover, all thesemethods have in common the need for large and powerful hydraulic jacksto overcome not only the skin friction of the pipes being installed, butalso an extra penetration force in order to be able to cut the ground infront of the cutting head.

One case of an auger boring machine is presented in U.S. Pat. No.4,013,134 (see FIG. 1). In general, the machine 100 comprises a base 101that includes spaced track members, which are disposed in a trenchadjacent to the hill to be bored. The machine also includes a framemounted for movement along the track means 102, and such carriage 103supports a power train for rotating connected sections of auger shafts104, which comprise a progressively extendable boring auger. The framesupports a pusher ring 105 for driving sections of casings into thebored hole, and an associated pushing cylinder is provided for advancingand retracting the frame and pusher ring along the track.

One disadvantage of this type of machine relies on the need for acomplete set of augers (at least same length of the total drive) with asimilar diameter of the pipe to be installed in order to drag the soilcoming from the cutting head to the jacking pit or entry shaft.Therefore, if a different project requires the installation of pipes ofa different diameter, in most of the cases, the whole auger set has tobe purchased again. Another disadvantage of using a continuous auger isthe high torque requirements of this type of system. The high torqueincreases the chances of injury or death for people working close to themachine since there is a risk that the machine will flip on its sidewhen facing tough grounds, smashing anything or anyone close to it. Thehigh torque requirements are a consequence of the torque needing to cutthe natural ground in front of the cutting head, the energy required tomove the whole set of augers inside the steel casings, and/or the torqueneeded to drag the spoils along all the installed pipes. This continuousauger-based spoil extraction system produces the drag of spoils as areaction produced by the spinning of those augers surrounded by thedirt. In this process, a considerable part of the energy is lost byfriction and by the radial force component resulting between the groundand the augers. Another issue with this method is that, in shallowinstallations or sandy soils, there is a risk of generating a sinkhole.

Other trenchless methods are related to micro-tunneling machines. Suchsystems involve a whole family of machines with some variations amongthem. Many of the variations differ on how the soil is excavated and howthe spoils are transported to the surface of the jacking shaft. Ingeneral terms, they include a boring shield that is pushed forward bythe product pipes behind it, which are being jacked by large and robusthydraulic jacks in the launch pit. As these micro-tunnel boring machinesmove forward through the ground, the soil is removed by typically mixingit with a fluid, to then pump the mixture out of the tunnel into aseparation plant, wherein the solids are separated from the fluids. Analternative way to transport the excavated soil is by the means of ashort auger located just behind of the cutting shield, filling bucketcarts that are continuously moving back and forward inside the tunnel,and carrying out the excavated material. These methods do not alwayswork well in shallow applications, depending on soil type. In addition,tunnel boring tends to be slow and expensive because of the type ofequipment required, and because the cutting shield is speciallymanufactured or selected based on the specifications of each project(e.g., a diameter of the pipe and ground conditions).

Alternatively, other methods are based on percussive impacts for rammingsteel pipes into the ground rather than using static jacking forces. Inmost of these cases, these steel pipes mostly are protective pipes foraccommodating the final carrier pipes inside of them. Normally, theseimpact-based methods have an open-end cutting edge at the front of thefirst pipe to let the ground coming in. Once the installation iscompleted, a procedure starts to mechanically, hydraulically,pneumatically or manually extract the ground inside the pipe. Oneexample of an impact-based method is the Paul Schmidt, U.S. Pat. No.4,671,703 (e.g., as shown in FIG. 2)

In one conventional approach to pipe ramming 200, a percussive pneumatichammer 201 is used to drive the pipe 202 horizontally or at an angleinto the ground. The hammer's housing is attached to the end of the pipeby means of a suitable fitting 203 and is sometimes further secured bycables. A piston-actuated ram strikes a plate inside the housing and thepercussive force is transmitted to the end of the pipe through thehousing, thereby causing the pipe to advance into the ground. Pneumaticrammers are characterized by producing several blows per minute,delivering low to medium energy on each blow. A typical small pneumatichammer offers 0.17 kJ of energy and delivers 580 blows per minute,weighing less than 10 kg. A typical large hammer has 40 kJ of energy,weighs 12 metric tons and delivers 180 blows per minute.

Hydraulic (rather than pneumatic) hammers are often used in verticaldrilling. This type of large hammers generally operates at fewer strokesper minute but delivers much more per blow. In this case, the strikepiston extends outside the hammer housing to strike the casing.Typically, one hydraulic hammer weighs 4 metric tons, delivers 65 blowsper minute at 30 kJ, while a 242 metric ton hammer delivers 2300 kJ at30 blows per minute. In vertical drilling, the hammer housing ismaintained in contact against the casing principally by means ofgravity. Even if they are not commonly used for horizontal pipe ramming,they are an alternative when installing large casing diameters. However,because the ram extends outside the hammer housing, it is not practicalto secure the housing to the pipe. It therefore becomes essential toprovide crowd of the hammer against the pipe. One approach 300 to doingso is disclosed by Verkyk, U.S. Pat. No. 6,652,190, which relies on acable winch crowd system 301 (see, e.g., FIG. 3A).

A recent improvement 302 of the Verkyk invention is disclosed by U.S.Patent Pub. No. 2016/0333642 to Bachand et al, in which the winch-basedcrowd is substituted by a carriage that is urged forward by hydrauliccylinders acting between the carriage and an abutment (see, e.g., FIG.3B). A compressive resilient assembly is mounted on the carriage 303 inorder to release its energy to the hydraulic hammer 304 to keep it incontact with the pipe 305 after each impact. Since this technologyemploys a hydraulic hammer, the space requirements for the entry pitwill be considerably larger than the space needed for other trenchlesstechniques, making this machine suitable mostly to large diameterinstallations (e.g., pipes over 72 inches in diameter), like in the caseof its predecessor (Verkyk, U.S. Pat. No. 6,652,190). Another deficiencyof the Bachand publication is that the penetration is essentiallygenerated by the hammer's impacts. In such a case, the hydraulic forceis used to keep the large hydraulic hammer in place (attached to thepipe) and not to counteract the natural pipe elasticity or to notablyincrease the penetration force. Furthermore, due to the high-energyimpact peaks generated by the hydraulic hammer, it is impractical toapply high static force to the pipe since this will lead to the use ofconsiderable thicker steel casings to avoid damages in the pipe.

Regardless the type of rammer used, one common problem with percussivepipe ramming methods (including Bachand) is that the soil-clearingprocess cannot be done at the same time with the installation process,leading to a reduction in overall productivity. Another common problemis the need of relatively high energy quantities (big hammers) toinstall the pipes or casings since a considerable part of the energy ofeach impact is lost. One relevant part of the energy is absorbed by thenatural steel pipe elasticity, and the pipe's external and internal skinfriction (from the soil coming inside) dissipates another important partof the energy. Additionally, due to the momentum transferred from therammer to the pipe, the extra mass added to the pipe due to the soilcoming inside it during operation diminishes the acceleration of thecutting edge, reducing the penetration force in the front of the firstpipe. All of these undesired effects are magnified as the length of thedrive increases, limiting this method to be useful only for relativelyfor short drives (normally less than 300 feet).

Furthermore, all of the above trenchless methods have their ownlimitations and applicability depending on the length, diameter,precision requirements and ground conditions. Moreover, all thesemachines are designed to overcome the maximum length and diameter inwhich they were preconceived, even if that means to be overpowered forshorter drives or smaller diameters. Finally, most of the machineslisted above (especially pipe jacking-based methods) have their mainparts specifically dimensioned for a specific pipe diameter, and everytime a new diameter has to be installed, a significant investment has tobe made in a new custom part.

SUMMARY

It is an object of some embodiments of the present invention to providea method and apparatus for installing pipe sections (e.g., steelcasings), or installing new product pipelines, without trenching theground between two pits or shafts. It is further an object of thepresent invention to provide a versatile method for trenchlessinstallations of new pipes, while being capable of reaching a wide rangeof diameters (e.g., up to 72 inches) and soil conditions, especiallyrisky ground conditions for many of the current technologies. Some ofthese tough conditions include unstable soils (e.g., cobble), sandy orgranular soils with presence of ground water, or highly heterogeneoussoils along the drive.

The features of some embodiments of the present invention conglomeratethe advantages of some known trenchless techniques. In one embodiment ofthis invention, a hydraulic jacking frame compresses and pushes thesteel pipes against the ground with a constant force, while percussionimpacts coming from a pneumatic rammer generate additional penetrationforce to move forward the pipes into the ground. The open-ended pipe inthe front lets the soil come inside it, while an independent lineardisplaceable soil-clearing system progressively removes the dirt whilethe installation progresses, reducing the total moving mass during theinstallation, and consequently augmenting the effectiveness of theimpacts. Since the open-ended pipe has minimal contact area with theground in front of it, the cutting edge allows the soil to enter intothe pipe with low requirements of penetration force, unlike in the caseof apparatus with rotational cutting heads in front of the first pipe.The impact force applied is maximized since constant hydraulic forceminimizes energy losses caused by the pipe bounce back (due to thenatural pipe's elasticity), while adding force to overcome the skinfriction of the pipe or casing. The pneumatic rammer generates lowerenergy peaks compared to a hydraulic hammer, at a higher frequency(e.g., from 160 to 580 blows per minute), and these lower energy peaksallow applying a higher static force to the pipes without the need touse thicker steel pipes.

In one embodiment, the main jacking frame comprises hydraulic cylindersacting on a rail-mounted pusher plate in which the percussive pneumaticrammer is firmly attached by means of a suitable fitting. The pusherplate works as a device for combining the impacts and the static forcein order to transform that energy into penetration force for the pipesin front of it, while maintaining the pipe at the desired alignment. Thefitting of the hydraulic rammer is slightly eccentric with respect tothe pipe's centerline in order to let the clearing rods (which arealigned to the centerline) pass through a window in the pusher plate toclear the dirt inside the pipes.

In another embodiment, the soil-clearing system includes clearing rods,at least one auger section, and a linear displaceable frame carrying ahydraulic motor on it. This frame is mounted on the same main jackingsystem's rails but with an independent set of hydraulic actuators forgoing forward and backward along those rails or tracks. Thedirt-extraction system of this invention differs from existingauger-based methods since, instead of dragging the dirt using only therotation of a continuous auger set, the system uses the rotation (whilegoing forward) of a few equally-distanced auger segments only to capturethe soil inside the pipe like the analogical case of a wine-bottleopener capturing a bottle's cork. Then, the segmented augers are pulledback with the dirt by using hydraulic jacks; this is an axialenergy-efficient process like in the analogical scenario of a standardwine-bottle opener using its arms to extract a bottle's cork instead ofusing rotation only. This process is progressively repeated in such amanner that each auger leaves behind the dirt after retracting thesystem, and then starts again going forward (while rotating) in order tocollect the dirt left behind by the following auger segment. Note thatthe bigger the separation between auger segments is, the longer thedisplacement of the whole clearing system is to perform this coordinatedtask. As an alternatively embodiment, this soil-clearing system can besubstituted by a continuous auger driven by a bigger hydraulic motorfixed at the main jacking frame, like a standard auger boring machine.This last configuration can require more torque and may need to replacethe whole auger set every time the diameter of the pipe changes, insteadof changing just a few auger segments. In some embodiments, the soilclearing system can include at least one clearing rod with one augersection, or alternatively, just one auger section attached directly tothe hydraulic motor.

Another feature of the present invention is the power optimizationcapability in which the independent linear displaceable soil-clearingsystem is used for generating a supplementary hydraulic jacking force,only when extra pushing force is needed. That is, pushing, with theirown hydraulic cylinders, the main jacking frame to increase the totalpushing force in order to overcome obstacles, high skin friction of longdrives, or hard soil conditions. The extraction of the excavatedmaterial is temporarily suspended when the clearing-soil system is usedfor pushing the jacking frame.

In one aspect, the invention features a system for installing pipeunderground. The system includes a pneumatic rammer configured toprovide a percussive force to a section of pipe. The system alsoincludes a main jacking frame coupled to the pneumatic rammer, the mainjacking frame including a surface for contacting the section of pipe.The system also includes one or more hydraulic jacks coupled to the mainjacking frame and configured to provide a hydraulic force to the sectionof pipe. The system also includes a set of tracks coupled to the mainjacking frame, the set of tracks permitting the main jacking frame toslide in a longitudinal direction.

In some embodiments, the system further includes a soil-clearing systemhaving a base frame coupled to the set of tracks. The soil-clearingsystem is configured to extract dirt from inside the section of pipeduring underground installation of the section of pipe. The base frameis slideable over the set of tracks independent of the main jackingframe. In some embodiments, the soil-clearing system includes arod-auger assembly driven by a hydraulic motor or another rotatingactuator to drag dirt during operation. In some embodiments, the mainjacking frame includes a pusher plate having at least one window topermit passage of dirt by the soil-clearing system.

In some embodiments, the soil-clearing system includes at least oneclearing rod, at least one auger section attached to the clearing rod,and an axially displaceable rail-mounted frame attached to the clearingrod, the rail-mounted frame carrying a hydraulic motor. In someembodiments, the rail-mounted frame moves forward and backward along thelongitudinal direction by means of at least one hydraulic cylinderacting between the rail-mounted frame and a locking system. In someembodiments, the at least one clearing rod, the at least one augersection, and the axially displaceable rail-mounted frame are configuredto extract dirt from sequential sections of pipe. In some embodiments,the pneumatic rammer is a high frequency rammer from 160 to 580 blowsper minute. In some embodiments, the section of pipe is steel. In someembodiments, the steel pipe acts as a steel casing for carrying otherpipes inside. In some embodiments, the section of pipe has a diameter of72 inches or less.

In another aspect, the invention features a method for installing pipeunderground. The method includes compressing, by a main jacking framecoupled to a set of tracks and assisted by at least one hydrauliccylinder, a section of pipe against a ground surface. The method alsoincludes generating, by a pneumatic rammer attached to the main jackingframe, a percussive impact for advancing the section of pipe into theground. The method also includes pushing, by the jacking frame and thepneumatic rammer, the pipes into the ground.

In some embodiments, the method further includes extracting, using asoil clearing system coupled to the set of tracks, dirt from inside thesection of pipe during installation of the section of pipe, the soilclearing system moveable with respect to the main jacking frame. In someembodiments, the main jacking frame includes a pusher plate having atleast one window to permit passage of dirt by the soil-clearing system.In some embodiments, the method further includes employing a hydraulicforce to pre-compress the section of pipe to counteract an elasticity ofthe section of pipe to promote efficient energy transmission from thepneumatic rammer through the section of pipe.

In some embodiments, a constant force is applied against the ground bythe jacking frame. In some embodiments, the method further includes,after the section of pipe is installed underground, joining one or moreadditional sections of pipe to the section of pipe to form anunderground tunnel between an entry point under the ground surface and atarget pit. In some embodiments, the pneumatic rammer is a highfrequency rammer from 160 to 580 blows per minute. In some embodiments,the soil-clearing system includes at least one clearing rod, at leastone auger section attached to the clearing rod, and an axiallydisplaceable rail-mounted frame attached to the clearing rod, therail-mounted frame including a hydraulic motor.

In some embodiments, the rail-mounted frame moves forward and backwardalong the longitudinal direction by means of at least one hydrauliccylinder acting between the rail-mounted frame and a locking system. Insome embodiments, the soil-clearing system includes at least twoclearing rods, each clearing rod having at least one auger section, theaxially displaceable rail-mounted frame configured to extract dirtsequentially in a coordinated movement of the at least two clearing rodsand auger sections. In some embodiments, the soil-clearing systemincludes an uninterrupted auger assembly driven by a hydraulic motor todrag dirt during operation.

In another aspect, the invention features a system for clearing soilfrom a section of pipe during underground installation. The systemincludes a main jacking frame including a surface for contacting thesection of pipe. The system also includes a set of tracks coupled to themain jacking frame, the set of tracks permitting the main jacking frameto slide along a longitudinal direction. The system also includes asoil-clearing system having a base frame coupled to the set of tracks,the soil-clearing system configured to extract dirt from inside thesection of pipe during underground installation of the section of pipe,the soil-clearing system moveable along the longitudinal directionindependent of the main jacking frame and including at least one augermounted in a frame coupled to the set of tracks that can move forwardand backward along the longitudinal direction independently of the mainjacking frame.

In another aspect, the invention features a method for clearing soilfrom a section of pipe during underground installation. The methodincludes extracting, using a soil clearing system coupled to a set oftracks, dirt from inside the section of pipe during installation of thesection of pipe, the soil clearing system slideable over the set oftracks. The soil-clearing system includes at least one clearing rod, atleast one auger section attached to the clearing rod, and an axiallydisplaceable rail-mounted frame attached to the clearing rod, therail-mounted frame including a hydraulic motor.

The foregoing may cover only some of the aspects of the invention. Otheraspects may be appreciated by reference to the following description ofat least one preferred mode for carrying out the invention in terms ofone or more examples. The following embodiment of the invention is not adefinition of the invention itself, but is only an example that embodiesthe inventive features of it.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate one embodiment of the inventionand together with the description, serve to explain the principles ofthis invention. In the drawings:

FIG. 1 is a side elevational view of a prior art method for auger boringshowing a steel pipe being installed underground, while a set of augersare transmitting torque to a cutting head, at the same time they areclearing the dirt inside the casing.

FIG. 2 is a side elevational view of a prior art method for pipe rammingshowing a steel pipe being inserted underground.

FIG. 3A is a top planar view of a prior art method for pipe rammingusing a hydraulic hammer and a cable winch crowd system.

FIG. 3B is an isometric view of a prior art method for pipe rammingusing a hydraulic hammer and a hydraulic crowd system.

FIG. 4A is an isometric view and a side elevation view of a schematicdiagram of a system for installing pipe underground, according to anillustrative embodiment of the invention.

FIG. 4B is a side elevation view of a schematic diagram of a system forinstalling pipe underground, according to an illustrative embodiment ofthe invention.

FIG. 5A is a top planar view of the details of an independent lineardisplaceable soil clearing system, according to an illustrativeembodiment of the invention.

FIG. 5B is a side elevation view of the details of an independent lineardisplaceable soil clearing system, according to an illustrativeembodiment of the invention.

FIG. 6A is a side elevation view with a cross section showing details ofthe non-continuous auger assembly for the soil clearing system,according to an illustrative embodiment of the invention.

FIG. 6B is an isometric exploded view showing details of thenon-continuous auger assembly for the soil clearing system, according toan illustrative embodiment of the invention.

FIG. 7A is a side elevation view with a partial cross section showingdetails of a self-anchoring system for the hydraulic jacks of the mainjacking frame, according to an illustrative embodiment of the invention.

FIG. 7B is a top planar view with a partial cross section of theinvention showing details of a self-anchoring system for the hydraulicjacks of the independent linear displaceable soil clearing system,according to an illustrative embodiment of the invention.

DETAILED DESCRIPTION

As shown in FIG. 4A, the rammer 10 is used to generate a cyclical force(e.g., a series of percussive impacts) to a rail-mounted main jackingframe 12. The rammer 10 may be driven percussively by a pneumatic hammeror other high frequency driving apparatus, acting on the main jackingframe 12 using any suitable fitting device (not shown). The rammer 10can be of the type manufactured by Hammerhead Trenchless Equipment,Model No. 12-(300)-AR. Other models of rammers could also be used. Thejacking frame is assisted by a set of hydraulic jacks 14, which addhydraulic pushing force to the main jacking frame 12. The main jackingframe 12 has a surface for contacting the casing 16 and transmits thepercussive force and the hydraulic force to the casing 16. The casingsection 16 may be substituted by any product pipe able to resist andtransmit the impact force generated by the rammer 10. The main jackingframe 12 is coupled and slides over the modular main tracks 18 which areassembled together to reach the desired stroke for the lineardisplacement of the main jacking frame 12, depending on the availablespace in the entry pit 20. During the pipe installation process, asoil-clearing system 22 (e.g., an independent, displaceablesoil-clearing system) is used to clear the soil coming inside the casingsection 16 while the installation progresses. The soil-clearing system22 brings the excavated material to the entry pit 20 by dragging itthrough an open section or window in the main jacking frame 12, lettingthe material being collected into an optional bucket cart 24 attached tothe main jacking frame 12. Once the bucket cart 24 is full of material,it can be removed from the main jacking frame 12 in order to dispose thematerial in a designated place on the surface. Alternatively, the spoilscan be dropped in the entry pit without that optional bucket cart 24, tobe collected later on manually or by means of an excavator machine.

FIG. 4B shows how the main tracks assembly is leaning on a support wall26 for counteracting the reaction forces generated when jacking thecasing sections 16 into the ground. Other types of anchoring methodscould also be used to maintain the main tracks 18 fixed to the entry pit20. Once one casing section 16 is installed, the last inserted clearingrod 28 is disengaged from the soil-clearing system 22, and both thesoil-clearing system 22 and the main jacking frame 12 are retracted totheir initial position in order to leave enough space to lay downanother casing section 16. An optional welding trench 30 may be used toaccommodate the welder man when welding between the two casing sections16. Other methodologies may also be used to join the casing sections 16.The process is repeated until the first casing section 16 reaches theexit pit 32.

FIG. 5A and FIG. 5B expose the details of the soil-clearing system 22which is a rail-mounted assembly of other subsystems explained asfollows. A base frame 22A is used to support the whole soil-clearingsystem and it is able to slide over the main tracks 18 withoutinterfering with the path of the jacking frame 12. The base frame 22Ahas short tracks attached in order to let slide over it top frame 22B.The relative linear displacement between base frame 22A and top frame22B is generated by means of another set of supplementary hydraulicjacks 22C. In order to avoid relative movement between the base frame22A and the main tracks 18, a supplementary self-anchoring system 22D isshown. However, the self-anchoring system can be substituted with anyanchoring systems such as manual locking levers, hydraulic locks,electric solenoids, or other locking devices. The top frame 22B alsoincludes a housing and a rotor mounted on taper roller bearings forsupporting radial and axial forces. The rotor of the top frame 22B isattached to the shaft of a hydraulic motor 22E, which provides rotationto the soil-clearing system. As shown in FIG. 6A, the torque provided byhydraulic motor 22E and the push/pull force are transmitted through thedetachable clearing rods 28. Each clearing rod 28 is provided with amale and a female connection and a hole in each connection in order toaccommodate a pin 38 for locking the clearing rod 28 to the next one. Aset of supplementary augers 34 can be progressively added to theclearing rods 28 assembly during the casing installation process. Fordrilling the compacted soil coming inside the first casing section 16,an auger bit 36 is installed in front of the first clearing rod 28.

FIG. 6A shows a cross section of a clearing rod 28—supplementary auger34 assembly. As it is shown, the supplementary augers 34 have an annularspace in order to accommodate inside it the clearing rod 28. Then thetwo pieces are joined together by the means of threaded pins 38. Othertype locking methods could also be used to fix the two parts together.FIG. 6B exemplifies how the clearing rods 28 and the supplementary auger34 are assembled using the threaded pins 38.

FIG. 7A shows a partial cross section of the main self-anchoring system40 of the main jacking frame 12, in which the main hydraulic jacks 14lean on to push or retract the main jacking frame 12. This component ofthe invention can be substituted with any anchoring systems such asmanual locking levers, hydraulic locks, electric solenoids, or anotherlocking component to provide a pushing point for the main hydraulicjacks 14. FIG. 7B also exposes a cross section of a detailed view forthe supplementary self-anchoring system 22D explained above. In bothself-anchoring systems, the operation mode is based on releasing thelock (also called dogs) from the main tracks 18, and then retract orexpand the hydraulic jacks in order to shift to another anchoring point.

Another feature of this invention is the possibility to increasehydraulic power used to push the main jacking frame 12 when needed byrelying on the supplementary hydraulic jacks 22C of the soil-clearingsystem 22. This is possible since the soil-clearing system 22 can moveindependently from the main jacking system.

Some embodiments of the present invention have been described above. Itis recognized, however, that departures may be made therefrom and thatobvious modifications could come to the mind of a person skilled in theart without departing from the scope of the invention.

What is claimed is:
 1. A system for installing pipe underground, thesystem comprising: a pneumatic rammer configured to provide a percussiveforce to a section of pipe; a main jacking frame coupled to thepneumatic rammer, the main jacking frame including a surface fordirectly contacting and compressing the section of pipe; one or morehydraulic jacks coupled to the main jacking frame and configured toprovide a static hydraulic force to the section of pipe, the statichydraulic force combining with the percussive force to drive the sectionof pipe underground; and a set of tracks coupled to the main jackingframe, the set of tracks permitting the main jacking frame to slide in alongitudinal direction.
 2. The system of claim 1 further including asoil-clearing system having a base frame coupled to the set of tracks,the soil-clearing system configured to extract dirt from inside thesection of pipe during underground installation of the section of pipe,the base frame slideable over the set of tracks independent of the mainjacking frame.
 3. The system of claim 2 wherein the soil-clearing systemincludes a rod-auger assembly driven by a hydraulic motor or anotherrotating actuator to drag dirt during operation.
 4. The system of claim2 wherein the main jacking frame includes a pusher plate having at leastone window to permit passage of dirt by the soil-clearing system.
 5. Thesystem of claim 2 wherein the soil-clearing system includes at least oneclearing rod, at least one auger section attached to the at least oneclearing rod, and an axially displaceable rail-mounted frame attached tothe at least one clearing rod, the rail-mounted frame carrying ahydraulic motor.
 6. The system of claim 5 wherein the rail-mounted framemoves forward and backward along the longitudinal direction by means ofat least one hydraulic cylinder acting between the rail-mounted frameand a locking system.
 7. The system of claim 5 wherein the at least oneclearing rod, the at least one auger section, and the axiallydisplaceable rail-mounted frame are configured to extract dirt fromsequential sections of pipe.
 8. The system of claim 1 wherein thepneumatic rammer is a high frequency rammer from 160 to 580 blows perminute.
 9. The system of claim 1 wherein the section of pipe is steel.10. The system of claim 1 wherein the section of pipe has a diameter of72 inches or less.
 11. A method for installing pipe underground, themethod comprising: compressing, by a main jacking frame coupled to a setof tracks and assisted by a static hydraulic force from at least onehydraulic cylinder, a section of pipe against a ground surface, the mainjacking frame directly contacting the section of pipe; generating, by apneumatic rammer attached to the main jacking frame, a percussive impactfor advancing the section of pipe into the ground; and pushing, by themain jacking frame and the pneumatic rammer, the section of pipe intothe ground, wherein the percussive impact and the static hydraulic forcecombine to drive the section of pipe underground.
 12. The method ofclaim 11 further including extracting, using a soil clearing systemcoupled to the set of tracks, dirt from inside the section of pipeduring installation of the section of pipe, the soil clearing systemmoveable with respect to the main jacking frame.
 13. The method of claim12 wherein the main jacking frame includes a pusher plate having atleast one window to permit passage of dirt by the soil-clearing system.14. The method of claim 11 further including employing a hydraulic forceto pre-compress the section of pipe to counteract an elasticity of thesection of pipe to promote efficient energy transmission from thepneumatic rammer through the section of pipe.
 15. The method of claim 11wherein a constant force is applied against the ground by the jackingframe.
 16. The method of claim 11 further including, after the sectionof pipe is installed underground, joining one or more additionalsections of pipe to the section of pipe to form an underground tunnelbetween an entry point under the ground surface and a target pit. 17.The method of claim 11 wherein the pneumatic rammer is a high frequencyrammer from 160 to 580 blows per minute.
 18. The method of claim 12wherein the soil-clearing system includes at least one clearing rod, atleast one auger section attached to the at least one clearing rod, andan axially displaceable rail-mounted frame attached to the at least oneclearing rod, the rail-mounted frame including a hydraulic motor. 19.The method of claim 18 wherein the rail-mounted frame moves forward andbackward along a longitudinal direction by means of at least onehydraulic cylinder acting between the rail-mounted frame and a lockingsystem.
 20. The method of claim 18 wherein the soil-clearing systemincludes at least two clearing rods, each clearing rod having at leastone auger section, the axially displaceable rail-mounted frameconfigured to extract dirt sequentially in a coordinated movement of theat least two clearing rods and the at least one auger section.
 21. Themethod of claim 12 wherein the soil-clearing system includes anuninterrupted auger assembly driven by a hydraulic motor to drag dirtduring operation.